In recent years, planetary science has seen a tremendous growth in new knowledge. Deposits of
water ice exist at the Moon's poles. Discoveries on the surface of Mars point to an early warm wet
climate, and perhaps conditions under which life could have emerged. Liquid methane rain falls on
Saturn's moon Titan, creating rivers, lakes, and geologic landscapes with uncanny resemblances to
Earth's. Comets impact Jupiter, producing Earth-sized scars in the planet's atmosphere. Saturn's poles
exhibit bizarre geometric cloud patterns and changes; its rings show processes that may help us
understand the nature of planetary accretion. Venus may be volcanically active. Jupiter's icy moons
harbor oceans below their ice shells: conceivably Europa's ocean could support life. Saturn's tiny moon
Enceladus has enough geothermal energy to drive plumes of ice and vapor from its south pole. Dust from
comets shows the nature of the primitive materials from which the planets and life arose. And hundreds of
new planets discovered around nearby stars have begun to reveal how our solar system fits into a vast
collection of others.

This report was requested by NASA and the National Science Foundation (NSF) to review the
status of planetary science in the United States and to develop a comprehensive strategy that will continue
these advances in the coming decade. Drawing on extensive interactions with the broad planetary science
community, the report presents a decadal program of science and exploration with the potential to yield
revolutionary new discoveries. The program will achieve long-standing scientific goals with a suite of
new missions across the solar system. It will provide fundamental new scientific knowledge, engage a
broad segment of the planetary science community, and have wide appeal for the general public whose
support enables the program.